Hybridoma antibodies that bind oligosaccharides are valuable reagents for analysis, localization, and purification of free oligosaccharides and glycoconjugates. We have developed immunization protocols and screening procedures, for producing hybridomas against oligosaccharides purified from human milk and urine. Many of these oligosaccharides are structurally identical with carbohydrate chains found in naturally-occurring glycolipids and glycoproteins. Hybridoma antibodies against a glucose-containing tetrasaccharide (G)4 with the structure G1cAlpha1-4G1cAlpha1-4G1c have been used in a radioimmunoassay to study the metabolic origin of the tetrasaccharide. The same anti (G)4 hybridoma antibodies have been used for affinity purification of the free oligosaccharide.